Plannable v9.6: Minor changes and fixes

New Feature

• Now in the schedule compare tab, the date selection bar will also appear at the top just like the normal mode.
  

Changes

• Credits of courses with Any Section will also be included now in the total credit calculation.
• Semester list now shows all available semesters (all the way back to Fall 2006) rather than the latest 10~15.

Fixes

• Fixed an internal bug of schedule computation that may occur under rare circumstances.

Internal Changes

• Continuous integration is migrated from Travis CI to GitHub Actions.